Primary monitor at boot question

[gdbleb]

Is there a second place to set the "primary monitor" on a dual monitor Mac mini setup?
I have 2 Dell 4K displays connected via USB-C - DP to a 2018(2020) Mac mini running Big Sur (had been Catalina).
Right side display is primary (in System Preferences) and has the menu bar at the top.
Left side display is switched between MacOS (DP) and a Windoze laptop (HDMI).
Once in a while I shutdown the Mac mini. On restart the initial logon screen always appears on the left display.
There must be low-level setting for the "primary" that is in force before the OS is completely initialised.
Thai can't be random.

 

[4sallypat]

I think I had a similar problem with my dual displays on the M1 Mini.

Here is what @chabig said to try:

How to change primary display using System Preferences article

I am now happy with the setup - USB-C port is now primary and HDMI port is extended.

 

[gdbleb]

Update.
I had changed Display System Preferences multiple times to no effect.
Cleared NVRAM and system finally behaved as set in System Pref at boot time.

 

[jazz1]

I think I had a similar problem with my dual displays on the M1 Mini.

Here is what @chabig said to try:

How to change primary display using System Preferences article

I am now happy with the setup - USB-C port is now primary and HDMI port is extended.

Wow! Wow! Wow! Thank you 4sallypat! I never knew this. It was driving me crazy on my M1Macmini with one USB-C monitor, and the second one running via HDMI.